Hydraulic control mechanism



May 19, 1942. J. H. PRATTHALQ 2 283,695

HYDRAULIC CONTROL MECHANISM Filed June 19, 1941 2 Sheets-Sheet 1JZmeJ/QnfyP/aff- GV/berf Edgar Manley A/berf Henry Godfrey l'r/fnqINVENTORS 'May 19, 1942. J. H. PRATT ETAL HYDRAULIC CONTROL MECHANISM 2Sheets-Sheet 2 Filed June 19, 1941 W Wm r Wmmm W mm H V 6.; i m E f a aJ G a I r N /y. m 5 4 4 7 8. m F 1 mm 8.... I T, 1 1 e I 6 MP 5.868 waLmw 1/ @L I. i Q

OFFICE HYDRAULIC CONTROL MECHANISM James Henry Pratt, Birmingham,Gilbert Edgar Manley, Earlswood, and Albert Henry Godfrey Girling,Edgbaston, Birmingham, England Application June 19, 1941, Serial No.398,850

In Great Britain June 5, 1940 3 Claims. (01. 60-545) This invention hasreference to improvements drawn to a larger scale, of the improved hyinhydraulic control mechanism and is concerned draulic control mechanismutilised in Fig. 1. particularly with hydraulic control mechanism Fig. 3is a cross-section of part of Fig, l, the of the kind wherein thecontrolling operation is section being taken on the plane indicated bythe performed through the agency of a piston and line A in the said Fig.1 looking in the direction cylinder mechanism common to the unit orunits of the arrow to said line and to be actuated and which piston andcylinder Fig. 4 is a fragmentary view in longitudinal mechanism isgenerally termed the master cylin- Vertical section of a modified formof the imder mechanism, proved hydraulic control mechanism illustratedIn connection with hydraulic control mechain Figs. 1-3.

nism of the said kind it is usual to embody with Like numerals ofreference indicate similar the master cylinder mechanism, means wherebyparts in the several views.

communication can be established between the Referring first to theconstruction illustrated interior of the master cylinder and a liquidresin Figs. 1-3, e b e pedal lever 5 s D ervoir, so that when the mastercylinder mechl5 otally connected to the lower end thereof-one nism is atrest liquid can pass from the master end of a rod 6 the other endwhereof is in abutcylinder to the liquid reservoir in the event of mentwith the outwardly presented portion of a the development of abnormalpressure in the master piston l which is .reciprocably mounted mastercylinder and so that liquid can pass from Within its master cylinder 8.This master cylinthe liquid reservoir for recuperation purposes der 8 isprovided adjacentto its closed end with in the event of a loss of liquidin the pipe line a port which communicates by way of a passage or in theevent'of the production of sub-atmos- 8a with the interior of a valvechamber 8b conpheric pressures in the master cylinder, and the stitutedby a vertical extension 80 of the cylinder present invention has for itsobject the provi- B. The walls of the passage 8a are provided sion ofimproved valve means for controlling with notches 8d for a purpose to beset out here communication as aforesaid, which is simple both inafterand the upper end of the said passage in construction andin operation.8a constitutes a lower seating for a ball Valve According to theinvention the improved hy It which is located within the valve chamb rat. draulic control mechanism of the kind herein- The ball valve I0 isof slightly less diameter before referred to is characterised in thatthere than the diameter of the .chamber 81) so that is disposed in theline of flow between the masthe said ball valve I0 is freelydisplaceable within ter cylinder and the transmission line or lines thechamber 81). For example if the ball valve to the unit or units to beactuated a valve cham- I0 is T55 of an inch in diameter the bore of theher which has communication not only with the chamber 8b may be .015 ofan inch larger in transmission line and with the master cylinder,diameter.

but also with the liquid reservoir and in that The upper end of thevalve chamber 8b is there is disposed within the said chamber, a closedby a screw plug ll having therein a cenvalve means which is displaced bythe surge of trally disposed passage which communicates with liquidwhich obtains upon the initiation of a a liquid reservoir l2 by way of apipe IZa, working stroke and caused to move with the flow Locatedbetween the lower end of the plug ll of liquid to close the means ofcommunication and a shoulder at the upper end of the valve between theliquid reservoir and the aforesaid chamber 81) are a relatively softwashe l3, a, valve chamber. metallic washer l4 and a resilient washer I5said The invention will now be described with par- Tesi1 ient Washerbeing disposed W a recessed ticular reference to the accompanyingdrawings 5 portlon the underside of the metal Washer which illustratethe invention in its application The metal washer Prevents undueformation of the resilient washer [5 as in the r k g gi g ope ated bramg means for event of any such tendency the ball valve l0 t h In thedrawings con acts w1t the lower edge of the hole in the metal washer I4and .hu 1 i h Fig. 1 1s a d1agrammat1c View mamly in section t s ave asany fun er deformation of the said resilient washer 15 but of anydraulica y p d brakmameans at the same time permitting an effectivesealing corporating the improved hydraulic control of t holetherethrough mechanism. Adjacent the upper end the valve chamber hasFig. 2 is a detail View, mainly in section and communication with outletpassages 8e, 8) which communicate by way of downwardly inclined pipelines l6 leading to the cylinders l7 containing the oppositely disposedpistons 18 for operating the brake shoes l9. The passages 8e, 8 openinto the chamber 8b at positions which are slightly below the ball valvel when it is in its uppermost position as indicated in dotted lines inFig. 2.

The master piston l co-operates with a spring 20 which tends to move thesaid master piston I to its out of action position and the brake shoesl9 co-operate with a pull-oil spring 2| in known manner.

The operation of the invention is as follows:

When the brakes are out of action the ball valve I!) under the action ofgravity rests on its seating at the upper end of the passage 811 butliquid is able to pass to and from the master cylinder 8 by way of thenotches 8d. When the pedal lever is moved for the purpose of applying thbrakes the associated movement of the master piston I within the mastercylinder 8 occasions a surge or impulsive flow of liquid in the valvechamber 82) which carries the ball valve it with it without anymeasurable increase in pressure and for a very small travel of the pedallever 5. Ultimately the liquid flow seats the ball valve ii! firmly onthe lower central portion of the resilient washer l5 so as to seal thehole therein and so cut off communication between the liquid reservoirl2 and the valve chamber 8b and the master cylinder 8. After thissealing has been achieved further movement of the master piston Idisplaces liquid to the cylinders H by way of the outlet passages 8e, 8and pipe lines is.

The use of a resilient washer l5 ensures effective sealing by the ballvalve it even should there be traces of solid foreign matter in theliquid and when the said washer 25 has been compressed to an extentwhich ensures effective seating of the ball valve iii furthercompression of the said washer is prevented by reason of the surface ofthe ball valve Iii coming into contact with the lower edge of the holethrough the metal washer The ball valve it is maintained on itsuppermost seat during braking byvirtue oi the pressure in the system.

When pressure on the pedal lever 5 is removed for releasing the brakes,the master piston l is moved rapidly to its out of action position at aspeed which exceeds the rate of liquid flow from the cylinders I? underthe action of the pull-oil springs 21 and as a consequenc pressure inthe valve chamber 312 falls below atmospheric pres sure so that the ballvalve it drop and comes to rest on its lowermost seating at the upperend of the passage lid.

The residue of liquid coming from the cylinders I! can thus pass freelyto the master cylinder 8 and/or to the reservoir l2 and because the ballvalve 59 is now below the outlet passages 86, iii no flow of liquidbetween thecylinders H and the reservoir i2 resultin from any causewhatsoever can cause the ball valve H) to move to cut ofi communicationwith the said reservoir The inclination of the pipe lines IS in themanner shown facilitates the escape to the reservoir and thence to theatmosphere of any air contained in the liquid.

In the modification illustrated in Fig. 4 the outlet passages 8e, 8enter the valve chamber 8b above the diametral plane of the ball valveliland consequently when the brake pressure is released the pressuredeveloped previously in the system together with the pressure of thehead oi liquid in the reservoir I2 acts on the top portion of the ballvalve l8 and tends to move the ball valve I 0 from its uppermostposition against any pressures existing in the master cylinder 8. Inthis modificationthe metal washer I 4 co-operates with a locating washer22.

It will be appreciated that with a hydraulic control mechanism ashereinbefore described any expansion or contraction of the liquid doesnot occasion in the system a pressure above or below that of theatmosphere when the brakes are out of action. Moreover the valve deviceis positive and quick in action regardless as to whether or not thepedal lever 5 is actuated slowly or quickly in order to apply the brakesand furthermore the valve device is not subject to failure throughleakage.

In addition since there is a continually open passage between thecylinders H and th reservoir i2 when the brakes are out of actionsubatmospheric pressures will not be created in the system. thuseliminating any tendency for air to be drawn from the atmosphere, pastthe pistons E3 into the said system.

Although in the embodiments described a ball valve is utilised a freelydisplaceable piston valve could be used if preferred and furthermore itwill be understood that the invention is equally applicable to hydraulicmeans for actuating mechanism other than vehicle brakes.

Having now described our invention what we claim and desire to secure onLetters Patent is:

1. In a hydraulic control mechanism, in combination, a master cylinder,a piston therefor, a reservoir having a vent to the atmosphere, a checkvalve connecting the master cylinder with the reservoir, having a valvemember that is normally in position to open communication between thereservoir and the master cylinder; and is moved to a posititon to closesaid communication by flow of iluid from the master cylinder to thereservoir, a unit to be actuated, and a transmission line leading tosaid unit and connected to said check valve at a point whosecommunication with the reservoir is unobstructed by the valve memberwhen the valve member is in said former position, and whosecommunication with the master cylinder is unobstructed by the valvemember when the valve member is in said latter position.

2. In a hydraulic control mechanism, in combination, a master cylinder,a piston therefor, a reservoir located above the master cylinder, havinga vent to the atmosphere, a check valve connecting the master cylinderwith the reservoir, having a ball valve member that is normally inposition to open communication between the reservoir and the mastercylinder and is moved to a position to close saidcommunication by flowof fluid from the master cylinder to the reservoir, said valve memberhaving a substantial travel between its open position and its closedposition, a unit to be actuated, and a transmission line leading to saidunit and connected to said check valve at a point whose communicationwith the reservoir is unobstructed by the valve member when the valvemember is in said former position, and whose communication with themaster cylinder is unobstructed by the valve member when the valvemember is in said latter position.

3. In a hydraulic control mechanism, in combination, a master cylinder,a piston therefor, a reservoir located above the master cylindenrhavinga vent to the atmosphere, a valve chamber having a port at its lower endleading to the master cylinder, and having a port at its upper endsurrounded by a resilient valve seat and leading to the reservoir, aball valve member in the valve chamber that is normally in position toopen communication between the reservoir and the master cylinder and ismoved onto said seat to close said communication by flow of fluid fromthe master cylinder to th reservoir, said resilient seat being backed bya rigid annular shoulder adapted to contact said valve member aftersufiicient compression of'said resilient valve seat to ensure effectivesealing, a unit to be actuated, and a transmission line leading fromsaid valve chamber to said unit.

JAMES HENRY PRATT. GILBERT EDGAR MAN LEY. ALBERT HENRY GODFREY GIRLING.

